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Results for “NONEQUILIBRIUM RADIATION”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Effects of precursor heating on chemical and radiation nonequilibrium viscous flow around a Jovian entry body

The influence of precursor heating on viscous chemical nonequilibrium radiating flow around a Jovian entry body is investigated. Results obtained for a 45-degree hyperboloid blunt body entering Jupiter's nominal atmosphere at zero angle of attack indicate that the nonequilibrium radiative heating rate is significantly higher than the corresponding equilibrium heating. The precursor heating, in general, increases the radiative and convective heating to the body, and this increase is slightly higher for the nonequilibrium conditions.

Tiwari, S. N.↗
NASA NTRS1978

Effects of precursor heating on chemical and radiative nonequilibrium viscous flow around a Jovian entry body

The influence of precursor heating on viscous chemical nonequilibrium radiating flow around a Jovian entry body is investigated. Results obtained for a 45 deg hyperboloid blunt body entering the Jupiter's nominal atmosphere at zero angle of attack indicate that the nonequilibrium radiative heating rate is significantly higher than the corresponding equilibrium heating. The precursors heating, in general, increases the radiative and convective heating to the body and this increase is slightly higher for the nonequilibrium conditions.

Tiwari, S. N.↗
NASA NTRS1994

Nonequilibrium radiation and chemistry models for aerocapture vehicle flowfields

The primary accomplishments of the project were as follows: (1) From an overall standpoint, the primary accomplishment of this research was the development of a complete gasdynamic-radiatively coupled nonequilibrium viscous shock layer solution method for axisymmetric blunt bodies. This method can be used for rapid engineering modeling of nonequilibrium re-entry flowfields over a wide range of conditions. (2) Another significant accomplishment was the development of an air radiation model that included local thermodynamic nonequilibrium (LTNE) phenomena. (3) As part of this research, three electron-electronic energy models were developed. The first was a quasi-equilibrium electron (QEE) model which determined an effective free electron temperature and assumed that the electronic states were in equilibrium with the free electrons. The second was a quasi-equilibrium electron-electronic (QEEE) model which computed an effective electron-electronic temperature. The third model was a full electron-electronic (FEE) differential equation model which included convective, collisional, viscous, conductive, vibrational coupling, and chemical effects on electron-electronic energy. (4) Since vibration-dissociation coupling phenomena as well as vibrational thermal nonequilibrium phenomena are important in the nonequilibrium zone behind a shock front, a vibrational energy and vibration-dissociation coupling model was developed and included in the flowfield model. This model was a modified coupled vibrational dissociation vibrational (MCVDV) model and also included electron-vibrational coupling. (5) Another accomplishment of the project was the usage of the developed models to investigate radiative heating. (6) A multi-component diffusion model which properly models the multi-component nature of diffusion in complex gas mixtures such as air, was developed and incorporated into the blunt body model. (7) A model was developed to predict the magnitude and characteristics of the shock wave precursor ahead of vehicles entering the Earth's atmosphere. (8) Since considerable data exists for radiating nonequilibrium flow behind normal shock waves, a normal shock wave version of the blunt body code was developed. (9) By comparing predictions from the models and codes with available normal shock data and the flight data of Fire II, it is believed that the developed flowfield and nonequilibrium radiation models have been essentially validated for engineering applications.

Carlson, Leland A.↗
NASA NTRS1992

An approximate local thermodynamic nonequilibrium radiation model for air

A radiatively coupled viscous shock layer analysis program which includes chemical and thermal nonequilibrium is used to calculate stagnation point flow profiles for typical aeroassisted orbital transfer vehicle conditions. Two methods of predicting local thermodynamic nonequilibrium radiation effects are used as a first and second order approximation to this phenomena. Tabulated results for both nitrogen and air freestreams are given with temperature, species, and radiation profiles for some air conditions. Two body solution results are shown for 45 and 60 degree hyperboloid bodies at 12 km/sec and 80 km altitude. The presented results constitute an advancement in the engineering modeling of radiating nonequilibrium reentry flows.

Gally, Thomas A.↗
NASA NTRS1992

An approximate local thermodynamic nonequilibrium radiation model for air

A radiatively coupled viscous shock layer analysis program which includes chemical and thermal nonequilibrium is used to calculate stagnation point flow profiles for typical aeroassisted orbital transfer vehicle conditions. Two methods of predicting local thermodynamic nonequilibrium radiation effects are used as a first and second order approximation to this phenomena. Tabulated results for both nitrogen and air freestreams are given with temperature, species, and radiation profiles for some air conditions. Two body solution results are shown for 45 and 60 degree hyperboloid bodies at 12 km/sec and 80 km altitude. The presented results constitute an advancement in the engineering modeling of radiating nonequilibrium reentry flows.

Gally, Thomas A.↗
NASA NTRS1991

Nonequilibrium radiative heating prediction method for aeroassist flowfields with coupling to flowfield solvers

A method for predicting radiation adsorption and emission coefficients in thermochemical nonequilibrium flows is developed. The method is called the Langley optimized radiative nonequilibrium code (LORAN). It applies the smeared band approximation for molecular radiation to produce moderately detailed results and is intended to fill the gap between detailed but costly prediction methods and very fast but highly approximate methods. The optimization of the method to provide efficient solutions allowing coupling to flowfield solvers is discussed. Representative results are obtained and compared to previous nonequilibrium radiation methods, as well as to ground- and flight-measured data. Reasonable agreement is found in all cases. A multidimensional radiative transport method is also developed for axisymmetric flows. Its predictions for wall radiative flux are 20 to 25 percent lower than those of the tangent slab transport method, as expected, though additional investigation of the symmetry and outflow boundary conditions is indicated. The method was applied to the peak heating condition of the aeroassist flight experiment (AFE) trajectory, with results comparable to predictions from other methods. The LORAN method was also applied in conjunction with the computational fluid dynamics (CFD) code LAURA to study the sensitivity of the radiative heating prediction to various models used in nonequilibrium CFD. This study suggests that radiation measurements can provide diagnostic information about the detailed processes occurring in a nonequilibrium flowfield because radiation phenomena are very sensitive to these processes.

Hartung, Lin C.↗
NASA NTRS1991

Stagnation point nonequilibrium radiative heating and the influence of energy exchange models

A nonequilibrium radiative heating prediction method has been used to evaluate several energy exchange models used in nonequilibrium computational fluid dynamics methods. The radiative heating measurements from the FIRE II flight experiment supply an experimental benchmark against which different formulations for these exchange models can be judged. The models which predict the lowest radiative heating are found to give the best agreement with the flight data. Examination of the spectral distribution of radiation indicates that despite close agreement of the total radiation, many of the models examined predict excessive molecular radiation. It is suggested that a study of the nonequilibrium chemical kinetics may lead to a correction for this problem.

Hartung, Lin C.↗
NASA NTRS1991

Stagnation Point Nonequilibrium Radiative Heating and the Influence of Energy Exchange Models

A nonequilibrium radiative heating prediction method has been used to evaluate several energy exchange models used in nonequilibrium computational fluid dynamics methods. The radiative heating measurements from the FIRE II flight experiment supply an experimental benchmark against which different formulations for these exchange models can be judged. The models which predict the lowest radiative heating are found to give the best agreement with the flight data. Examination of the spectral distribution of radiation indicates that despite close agreement of the total radiation, many of the models examined predict excessive molecular radiation. It is suggested that a study of the nonequilibrium chemical kinetics may lead to a correction for this problem.

Hartung, Lin C.↗
NASA NTRS1981

Influence of nonequilibrium radiation and shape change on aerothermal environment of a Jovian entry body

The influence of nonequilibrium radiative energy transfer and the effect of probe configuration changes on the flow phenomena around a Jovian entry body are investigated. The radiating shock layer flow is assumed to be axisymmetric, viscous, laminar and in chemical equilibrium. The radiative transfer equations are derived under nonequilibrium conditions which include multilevel energy transitions. The equilibrium radiative transfer analysis is performed with an existing nongray radiation model which accounts for molecular band, atomic line, and continuum transitions. The nonequilibrium results are obtained with and without ablation injection in the shock layer. The nonequilibrium results are found to be greatly influenced by the temperature distribution in the shock layer. In the absence of ablative products, the convective and radiative heating to the entry body are reduced under nonequilibrium conditions. The influence of nonequilibrium is found to be greater at higher entry altitudes. With coupled ablation and carbon phenolic injection, 16 chemical species are used in the ablation layer for radiation absorption. Equilibrium and nonequilibrium results are compared under peak heating conditions.

Tiwari, S. N.↗
NASA NTRS1984

Calculation of nonequilibrium radiation in the flight regimes of aeroassisted orbital transfer vehicles

A computer code has been developed that calculates radiative properties of nonequilibrium air in the low-density regimes expected during the flight of aeroassisted, orbital transfer vehicles. From the given nonequilibrium thermodynamic state variables, the code calculates number densities of internal states and the accompanying emission and absorption characteristics. In addition, the code calculates the number density of the hypothetical gas in radiative equilibrium that produces the same radiation emission as the given nonequilibrium gas. Sample results are shown to demonstrate how the code predicts the nonlinear variation of radiation with density at low densities.

Park, C.↗
NASA NTRS1985

Calculation of Nonequilibrium Radiation in the Flight Regimes of Aeroassisted Orbital Transfer Vehicles

A computer code has been developed that calculates radiative properties of nonequilibrium air in the low-density regimes expected during the flight of aeroassisted, orbital transfer vehicles. From the given nonequilibrium thermodynamic state variables, the code calculates number densities of internal states and the accompanying emission and absorption characteristics. In addition, the code calculates the number density of the hypothetical gas in radiative equilibrium that produces the same radiation emission as the given nonequilibrium gas. Sample results are shown to demonstrate how the code predicts the non-linear variation of radiation with density at low densities.

Park, Chul↗
NASA NTRS1975

Estimates of nonequilibrium radiation for Venus entry

The present investigation is an analysis of the radiation from the chemical nonequilibrium region in the shock layer about a vehicle during Venus entry. The radiation and the flow were assumed to be uncoupled. An inviscid, nonequilibrium flowfield was calculated and an effective electronic temperature was determined for the predominant radiating species. Species concentrations and electronic temperature were then input into a radiation transport code to calculate heating rates. The present results confirm earlier investigations which indicate that the radiation should be calculated using electronic temperatures for the radiating species. These temperatures are not related in a simple way to the local translational temperature. For the described mission, the nonequilibrium radiative heating rate is approximately twice the corresponding equilibrium value at peak heating.

Grose, W. L.↗
NASA NTRS1991

Development of a nonequilibrium radiative heating prediction method for coupled flowfield solutions

A method for predicting radiation in thermochemical nonequilibrium flows has been developed. A summary of the development is presented, with emphasis on its unique features. The optimization of the method to provide efficient solutions allowing coupling to flowfield solvers is discussed. Representative results are obtained and compared to previous solutions and flight data. The method is found to be a useful tool for studies of nonequilibrium flowfields.

Hartung, Lin C.↗
NASA NTRS1991

Nonequilibrium radiation and chemistry models for aerocapture vehicle flowfields, volume 1

The following subject areas are covered: the development of detailed nonequilibrium radiation models for molecules along with appropriate models for atoms; the inclusion of nongray radiation gasdynamic coupling in the VSL (Viscous Shock Layer) code; the development and evaluation of various electron-electronic energy models; and an examination of the effects of shock slip.

Carlson, Leland A.↗
NASA NTRS1990

Nonequilibrium radiation and chemistry models for aerocapture vehicle flowfields

The primary tasks during January 1990 to June 1990 have been the development and evaluation of various electron and electron-electronic energy equation models, the continued development of improved nonequilibrium radiation models for molecules and atoms, and the continued development and investigation of precursor models and their effects. In addition, work was initiated to develop a vibrational model for the viscous shock layer (VSL) nonequilibrium chemistry blunt body engineering code. Also, an effort was started associated with the effects of including carbon species, say from an ablator, in the flowfield.

Carlson, Leland A.↗